How to Use Firestore with Python: Simple Guide

To use Firestore with Python, install the google-cloud-firestore library, set up authentication with a service account key, then create a Firestore client in your Python code to read and write data. Use client.collection() to access collections and document() to work with documents.

Syntax

Here is the basic syntax to connect and use Firestore in Python:

• Import library: Import Firestore client from google.cloud.
• Create client: Initialize Firestore client to connect to your database.
• Access collection: Use client.collection('collection_name') to get a collection reference.
• Access document: Use collection.document('doc_id') to get a document reference.
• Set data: Use document.set(data_dict) to write data.
• Get data: Use document.get() to read data.

python

from google.cloud import firestore

# Initialize Firestore client
client = firestore.Client()

# Reference a collection
collection_ref = client.collection('users')

# Reference a document
doc_ref = collection_ref.document('user_123')

# Set data in document
doc_ref.set({'name': 'Alice', 'age': 30})

# Get data from document
doc = doc_ref.get()
if doc.exists:
    print(doc.to_dict())

Output

{'name': 'Alice', 'age': 30}

Example

This example shows how to add a user document to Firestore and then read it back.

python

from google.cloud import firestore

# Create Firestore client
client = firestore.Client()

# Add a new user document
user_ref = client.collection('users').document('user_001')
user_ref.set({
    'name': 'John Doe',
    'email': '[e-mail]',
    'age': 28
})

# Retrieve the user document
user_doc = user_ref.get()
if user_doc.exists:
    print('User data:', user_doc.to_dict())
else:
    print('No such document!')

Output

User data: {'name': 'John Doe', 'email': '[e-mail]', 'age': 28}

Common Pitfalls

Common mistakes when using Firestore with Python include:

• Not setting up authentication with a service account JSON key or not setting the GOOGLE_APPLICATION_CREDENTIALS environment variable.
• Using incorrect collection or document names causing DocumentReference errors.
• Trying to read a document that does not exist without checking doc.exists.
• Forgetting to install the google-cloud-firestore package.

Always check for document existence before accessing data and ensure authentication is properly configured.

python

import os

# Wrong: No authentication setup
from google.cloud import firestore
client = firestore.Client()  # This will fail if credentials are missing

# Right: Set environment variable for credentials
os.environ['GOOGLE_APPLICATION_CREDENTIALS'] = '/path/to/service-account.json'
client = firestore.Client()  # Now works with proper auth

Quick Reference

Here is a quick reference for common Firestore Python client methods:

Method	Description
firestore.Client()	Creates a Firestore client to connect to the database
client.collection('name')	Gets a reference to a collection
collection.document('id')	Gets a reference to a document
document.set(data)	Writes data to a document
document.get()	Reads data from a document
document.update(data)	Updates fields in a document
document.delete()	Deletes a document

Key Takeaways

Install and import the google-cloud-firestore library to use Firestore with Python.

Set up authentication using a service account JSON key and the GOOGLE_APPLICATION_CREDENTIALS environment variable.

Use client.collection() and document() to access Firestore data.

Always check if a document exists before reading its data.

Handle common errors by verifying collection/document names and authentication setup.